This invention relates to a developer and a developing method for a light-sensitive lithographic printing plate, and developer composition for light-sensitive material, particularly to a developer which can develop well commonly the negative-type and the positive type light-sensitive lithographic printing plate, and a developer composition which can suitably develop a wash-off type light-sensitive material having a water-insoluble image forming layer.
In the prior art, for the negative-type light-sensitive lithographic printing plate (hereinafter called the negative-type PS plate) and the positive-type lithographic printing plate (hereinafter called the positive-type PS plate), the compositions of the developers were different, and developing could be done suitably only with the respective developers. If developing can be effected with a developer which is not the developer for exclusive use, no lithographic printing plate having sufficient performance can be obtained, and under the present status it is substantially impossible to effect commonly well the processing of the negative-type PS plate and the positive-PS plate with a developer of the same recipe.
Japanese Provisional Patent Publication No. 64351/1985 discloses a common developing method in which the negative-type PS plate and the positive-type-PS plate are both developed with one automatic developing machine. However, this technique performs developing with the respective developers for exclusive use successively in separate developing zones, and does not perform developing with a developer of the same recipe.
Accordingly, since the respective developers for exclusive use are used, management of solutions is cumbersome and it is difficult to perform stable developing for a long time.
A developer which performs common developing with one kind of developer is disclosed in Japanese Provisional Patent Publication No. 237442/1985. This developer comprises an organic solvent of ethylene glycol monophenyl ether or ethylene glycol monobenzyl ether, a silicate, an alkali metal hydroxide, an anionic surfactant and a water-soluble reducing agent. However, such developer is extremely susceptible to foaming, and the developing speed was not sufficiently rapid for the negative-type PS plate. On the other hand, when the positive-type PS plate is developed, developing latitude was liable to change extremely the developing result, whereby a part of the image portion was corroded during developing to be under the state readily defected. This tendency is more marked when the developing time is slightly elongated, or when the developing temperature is slightly higher than the predetermined temperature, thereby causing sometimes defect of the fine portion of the image, and also poor printing resistance during printing.
On the other hand, the so-called wash-off type light-sensitive material which obtains a relief image by removing the non-image portion in development after imagewise exposure has been utilized in many uses, and as said light-sensitive material, there are, for example, resin letterpress, light-sensitive lithographic plate, (PS plate), resist for print wiring, non-silver salt lith-film, light-sensitive peel mask film, color proof film, dry film, etc. When these light-sensitive materials are to be developed, it is recently frequently practiced from the standpoint of pollution, safety and hygiene to process an aqueous developer of an alkali aqueous solution. However, light-sensitive materials contain lipophilic substances insoluble or difficultly soluble in water or alkali aqueous solution in many cases, and therefore development can proceed with difficulty, whereby it takes too much time for removal of the non-image portion or the image remains to be undeveloped in some cases. Also, the components removed cannot be sufficiently dissolved but float in the solution, whereby contamination may be sometimes caused by attachment of the floating components on the image portion and the non-image portion.
For solving this problem, the techniques of adding an organic solvent or a surfactant have been known as disclosed in Japanese Provisional Patent Publications No. 44202/1978 and No. 86328/1979 or the technique of using a specific organic carboxylic acid as disclosed in U.S. Pat. Nos. 4,579,811 and 3,891,439.
These techniques are directed to improvement of developability, but they are still insufficient, and moreover undesirable from the standpoint of odor, pollution, safty and hygiene for the necessity to use an organic solvent to some extent, and use of surfactant in large amount sometimes posed a problem in foaming.